Can you develop resistance to valacyclovir?
Resistance usually develops due to mutations in the thymidine kinase pathway that cause patients to become non-sensitive to acyclovir and its pro-drug valacyclovir, according to Dr. Thimons.
Can herpes become resistant to valacyclovir?
Acyclovir resistance is not common but does occur at higher rates in immunocompromised patients. Acyclovir resistance can be attributed to thymidine kinase mutations and confers cross-resistance among the antiviral nucleoside analogs (acyclovir, valacyclovir, famciclovir, and penciclovir).
Do antivirals create resistance?
Prolonged antiviral drug exposure and ongoing viral replication due to immunosuppression are key factors in the development of antiviral drug resistance, which may manifest as persistent or increasing viremia or disease despite therapy.
How common is acyclovir resistance?
In spite of the distribution of over 2.3 × 106 kg of these nucleoside analogues, the prevalence of acyclovir resistance in herpes simplex virus isolates from immunocompetent hosts has remained stable at approximately 0.3%.
Why acyclovir is not working?
In some cases, herpes flare-ups do not respond to acyclovir, valacyclovir or famciclovir, probably due to resistant forms of HSV-1 and HSV-2. People living with HIV with suppressed immune systems—CD4 counts below 100—who have been on long-term acyclovir have developed drug-resistant herpes.
What to do if acyclovir isn’t working?
If the response is poor, the dose of oral ACV should be increased to 800 mg five times a day. If no response seen after 5 to 7 days, it is unlikely that the lesion will respond to intravenous ACV (or chemically and structurally related drugs such as VCV or famciclovir), so an alternative regimen must be assigned.
Can herpes virus become resistant to acyclovir?
Only three cases of clinical resistance of HSV to acyclovir have been reported. However, the incidence in immunocompromised patients, particularly those with AIDS and those who have had bone marrow transplants, is increasing.
Can a virus become resistant?
A resistance mutation is a mutation in a virus gene that allows the virus to become resistant to treatment with a particular antiviral drug. The term was first used in the management of HIV, the first virus in which genome sequencing was routinely used to look for drug resistance.
What causes virus resistance?
Biological basis of resistance This phenotype is determined by specific mutations in the viral genome (the genotype), which leads to alterations in the viral target protein (for example, HIV reverse transcriptase) or the viral drug activator (for example, herpes simplex thymidine kinase).
What happens if acyclovir doesnt work?
In order to suppress the infection, the tablet has to be taken daily. This tends to be an expensive form of treatment and so a generic form of the drug should be requested if cost is a problem. It works very well though, and will relieve your frustration.
Is there an alternative to acyclovir?
Famciclovir has also been shown to be effective at controlling oral herpes and genital herpes in people with compromised immune systems, and it’s occasionally prescribed as an alternative to valacyclovir and acyclovir in those cases.
